1. Field of the Invention
The present application relates to a fuel cell system.
2. Discussion of the Background
Recently, efforts have been directed to the development of fuel cells, which generate electricity as they are supplied with hydrogen (fuel gas) and air containing oxygen (oxidant gas). Fuel cells are a promising power source for applications such as fuel cell vehicles (mobile units).
A fuel cell produces water (water vapor) at its cathode during operation. In addition, for example, air flowing toward the cathode is humidified by a humidifier to maintain adequate moisture in an electrolyte membrane (solid polymer membrane) of a membrane electrode assembly (MEA) forming the fuel cell. Accordingly, water (water vapor, condensed water) remains in the fuel cell immediately after shutdown. Such water may freeze in the fuel cell at low temperatures (e.g., 0° C. or lower) after shutdown.
One proposed technique is to scavenge water from the fuel cell with a scavenge gas such as air if the fuel cell possibly freezes at low temperatures (see Japanese Unexamined Patent Application Publication No. 2007-123040).